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Two new methods for transforming priority queues into doubleended priority queues
 CPH STL Report
, 2006
"... Abstract. Two new ways of transforming a priority queue into a doubleended priority queue are introduced. These methods can be used to improve all known bounds for the comparison complexity of doubleended priorityqueue operations. Using an efficient priority queue, the first transformation can pr ..."
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Abstract. Two new ways of transforming a priority queue into a doubleended priority queue are introduced. These methods can be used to improve all known bounds for the comparison complexity of doubleended priorityqueue operations. Using an efficient priority queue, the first transformation can produce a doubleended priority queue which guarantees the worstcase cost of O(1) for findmin, findmax, and insert; and the worstcase cost of O(lg n) including at most lg n + O(1) element comparisons for delete, but the data structure cannot support meld efficiently. Using a meldable priority queue that supports decrease efficiently, the second transformation can produce a meldable doubleended priority queue which guarantees the worstcase cost of O(1) for findmin, findmax, and insert; the worstcase cost of O(lg n) including at most lg n + O(lg lg n) element comparisons for delete; and the worstcase cost of O(min {lg m, lg n}) for meld. Here, m and n denote the number of elements stored in the data structures prior to the operation in question, and lg n is a shorthand for log 2 (max {2, n}). 1.
Project proposal: A meldable, iteratorvalid priority queue, CPH
, 2005
"... Abstract. The Standard Template Library (STL) is a library of generic algorithms and data structures that has been incorporated in the C++ standard and ships with all modern C++ compilers. In the CPH STL project the goal is to implement an enhanced edition of the STL. The priorityqueue class of the ..."
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Abstract. The Standard Template Library (STL) is a library of generic algorithms and data structures that has been incorporated in the C++ standard and ships with all modern C++ compilers. In the CPH STL project the goal is to implement an enhanced edition of the STL. The priorityqueue class of the STL is just an adapter that makes any resizable array to a queue in which the elements stored are arranged according to a given ordering function. In the C++ standard no compulsory support for the operations delete(), increase(), or meld() is demanded even if those are utilized in many algorithms solving graphtheoretic or geometric problems. In this project, the goal is to implement a CPH STL extension of the priorityqueue class which provides, in addition to the normal priorityqueue functionality, the operations delete(), increase(), and meld(). To make the first two of these operations possible, the class must also guarantee that external references to compartments inside the data structure are kept valid at all times.
Putting your data structure on a diet
 In preparation (2006). [Ask Jyrki for details
, 2007
"... Abstract. Consider a data structure D that stores a dynamic collection of elements. Assume that D uses a linear number of words in addition to the elements stored. In this paper several datastructural transformations are described that can be used to transform D into another data structure D ′ that ..."
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Abstract. Consider a data structure D that stores a dynamic collection of elements. Assume that D uses a linear number of words in addition to the elements stored. In this paper several datastructural transformations are described that can be used to transform D into another data structure D ′ that supports the same operations as D, has considerably smaller memory overhead than D, and performs the supported operations by a small constant factor or a small additive term slower than D, depending on the data structure and operation in question. The compaction technique has been successfully applied for linked lists, dictionaries, and priority queues.
RankRelaxed Weak Queues: Faster than Pairing and Fibonacci Heaps?
, 2009
"... A runrelaxed weak queue by Elmasry et al. (2005) is a priority queue data structure with insert and decreasekey in O(1) as well as delete and deletemin in O(log n) worstcase time. One further advantage is the small space consumption of 3n + O(log n) pointers. In this paper we propose rankrelaxe ..."
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A runrelaxed weak queue by Elmasry et al. (2005) is a priority queue data structure with insert and decreasekey in O(1) as well as delete and deletemin in O(log n) worstcase time. One further advantage is the small space consumption of 3n + O(log n) pointers. In this paper we propose rankrelaxed weak queues, reducing the number of rank violations nodes for each level to a constant, while providing amortized constant time for decreasekey. Compared to runrelaxed weak queues, the new structure additionally gains one pointer per node. An empirical evaluation shows that the implementation can outperform Fibonacci and pairing heaps in practice even on rather simple data types.
Miniproject: Safe standardlibrary containers
"... Abstract. In this project the goal is to develop the safe * family of containers for the CPH STL. The containers to be developed should be safer and more reliable than any of the existing implementations. A special focus should be put on strong exception safety since none of the existing prototypes ..."
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Abstract. In this project the goal is to develop the safe * family of containers for the CPH STL. The containers to be developed should be safer and more reliable than any of the existing implementations. A special focus should be put on strong exception safety since none of the existing prototypes available at the CPH STL can give this guarantee for all operations. In spite of the safety requirements, the strict runningtime requirements specified in the C++ standard, and additional requirements specified in the CPH STL design documents, must be fulfilled.